1. Technical Field
The invention relates to a device for testing the permeability of fluids and/or vapors through elastomeric seal bodies.
2. Related Art
As a consequence of new legislation, the permeation of substances through sealing systems has become an important consideration when developing new seal bodies. This applies not only to all the sealing zones in the motor area, for example in respect to fuel permeation, but also to the development of new systems such as fuel cells (hydrogen permeation). In the area of sealing technology permeation rates are currently measured mainly on material samples or by testing complete systems such as tank systems. Usually, a measuring chamber only allows one single sample to be analyzed at any one time. To obtain meaningful permeation data, measurements need to be performed over longer time periods, thereby maintaining the measuring devices occupied with a single analysis for a long time.
The VDA guideline 675245 (Elastomeric components in motor vehicles—Test procedures for determining characteristics: permeability of fluids and vapors through elastomers) describes a test device to measure permeation through material samples using a simple setup (cup test). In this test small containers are first filled with a test medium (e.g. regular fuel mixture). The disk shaped material sample is then introduced into a recess provided on the container. A lid facing the container and providing a screwed connection to it includes a recess on the side of the sample to incorporate a support filter screen aimed at absorbing the internal pressure on the sample, if the test is carried out at elevated temperatures. The lid is provided with a passage allowing the test medium to pass through. The procedure begins with the registration of the initial weight of the container, including its content. If the fluid or the vapor-air mixture escape through the material sample, a reduction of the starting weight will be registered. The weight difference is a direct function of the amount escaped through permeation. The VDA guideline deals exclusively with material samples with a thickness of 2+/−0.1 mm, which is not consistent with the real operating conditions of the respective seal body. The recess provided on the container for holding the material sample is 1.5 mm deep, meaning that the material sample needs to be compressed by 25% by tightening the planar face of the container and the planar face of the lid against each respective side of the material sample. The extent to which the fluid or vapor-air mixture passes through the sample depends on the size of the passage on the lid—which does not correlate with real operating conditions—and the measured value will therefore not apply to a seal body under real installation conditions.